In a hard disk drive, a slider is often suspended just above a magnetic medium that is rotated to allow magnetic transducers in the slider to read (e.g., the reader) information from, and write (e.g., the writer) information to, the medium. The closer the slider can be positioned to the top surface of the medium/disk, which is typically a lubricant layer, the better the recording performance of the drive. Dynamic flying-height control technology involves positioning a heater within the slider that when activated can create a strategic bulge in the bottom surface (e.g., air bearing surface or ABS) of the slider thereby bringing the reader and the writer closer to the medium/disk top surface. The application of dynamic flying-height control technology can reduce the clearance of the magnetic heads (e.g., the reader and writer) from the disk surface to a few nanometers. However, lubricant pickup on the slider surface from the disk surface sometimes occurs as they are brought close together at the head disk interface (HDI) with a clearance of a few nanometers. This lubricant pickup can degrade the performance of the hard disk drive and/or cause it to fail.
Recently, ultraviolet (UV) treatment was applied to a lubricant coating on a carbon based overcoat layer of the media to increase the bonding ratio between the lubricant and the overcoat, and to thereby reduce lubricant pickup. One of the inventors studied the bonding mechanism of ultrathin perfluoropolyether (PFPE) lubricant films with hydroxyl end groups by measuring the bonding film thickness after UV irradiation (see article by H. Tani, et al., “Bonding Mechanism of Perfluoropolyether Lubricant Film with Functional Endgroup on Magnetic Disks by Ultraviolet Irradiation”, Tribol. Lett. (2012) 45:117-122, the entire content of which is incorporated by reference herein). The results of this study suggest the occurrence of three kinds of mechanisms. First, lubricants with hydroxyl end groups bond because of the photo-dissociation of the end groups by the UV light. Second, they bond because of the interaction between the end groups and the photoelectron from the carbon surface generated by UV irradiation. Third, they bond because of the photo-dissociation of the main chain by the UV light. In contrast, the dynamic reaction coordinate calculations suggest that the end groups in the PFPE lubricant dissociate because of the electron capture by the lubricant. As a result, the study inferred that the bonding of PFPE lubricant films with hydroxyl end groups on magnetic disks occurs by selective dissociation of the end groups because of UV irradiation. So while UV irradiation may increase the bonding ratio to reduce lubricant pickup, there is room for further improvements in the lubricant bonding process. Accordingly, methods for further reducing or avoiding lubricant pickup by improved lubricant bonding are needed.